Department of Molecular Biosciences and Bioengineering, University of Hawaii at Manoa, Honolulu, Hawaii, United States of America.
PLoS One. 2010 Oct 21;5(10):e13557. doi: 10.1371/journal.pone.0013557.
A close interconnection between nutrient metabolism and virulence factor expression contributes to the pathophysiology of Pseudomonas aeruginosa as a successful pathogen. P. aeruginosa fatty acid (FA) degradation is complicated with multiple acyl-CoA synthetase homologs (FadDs) expressed in vivo in lung tissue during cystic fibrosis infections. The promoters of two genetically linked P. aeruginosa fadD genes (fadD1 and fadD2) were mapped and northern blot analysis indicated they could exist on two different transcripts. These FadDs contain ATP/AMP signature and FA-binding motifs highly homologous to those of the Escherichia coli FadD. Upon introduction into an E. coli fadD(-)/fadR(-) double mutant, both P. aeruginosa fadDs functionally complemented the E. coli fadD(-)/fadR(-) mutant, allowing degradation of different chain-length FAs. Chromosomal mutagenesis, growth analysis, induction studies, and determination of kinetic parameters suggested that FadD1 has a substrate preference for long-chain FAs while FadD2 prefers shorter-chain FAs. When compared to the wild type strain, the fadD2 mutant exhibited decreased production of lipase, protease, rhamnolipid and phospholipase, and retardation of both swimming and swarming motilities. Interestingly, fadD1 mutant showed only increased swarming motility. Growth analysis of the fadD mutants showed noticeable deficiencies in utilizing FAs and phosphatidylcholine (major components of lung surfactant) as the sole carbon source. This defect translated into decreased in vivo fitness of P. aeruginosa in a BALB/c mouse lung infection model, supporting the role of lipids as a significant nutrient source for this bacterium in vivo.
营养代谢与毒力因子表达之间的紧密联系有助于铜绿假单胞菌成为成功的病原体。铜绿假单胞菌脂肪酸 (FA) 降解伴随着多种酰基辅酶 A 合成酶同源物 (FadD) 在囊性纤维化感染期间在肺组织中体内表达而变得复杂。两个遗传上相关的铜绿假单胞菌 fadD 基因（fadD1 和 fadD2）的启动子被定位，并且Northern blot 分析表明它们可能存在于两种不同的转录物上。这些 FadD 含有与大肠杆菌 FadD 高度同源的 ATP/AMP 签名和 FA 结合基序。当引入大肠杆菌 fadD(-)/fadR(-) 双突变体时，两种铜绿假单胞菌 fadD 都能够在功能上补充大肠杆菌 fadD(-)/fadR(-) 突变体，允许不同链长 FA 的降解。染色体诱变、生长分析、诱导研究和动力学参数的确定表明，FadD1 对长链 FA 具有底物偏好，而 FadD2 则偏好短链 FA。与野生型菌株相比，fadD2 突变体表现出脂酶、蛋白酶、鼠李糖脂和磷脂酶产生减少，以及游泳和群集运动能力延迟。有趣的是，fadD1 突变体仅表现出增强的群集运动能力。fadD 突变体的生长分析表明，它们在利用 FA 和磷脂酰胆碱（肺表面活性剂的主要成分）作为唯一碳源方面存在明显缺陷。这种缺陷转化为铜绿假单胞菌在 BALB/c 小鼠肺部感染模型中的体内适应性降低，支持脂质作为该细菌体内重要营养源的作用。
